The present invention relates to a slitter-winder of a fiber web production line in general and in particular to a method for calibrating the position of the slitter blades of a slitter-winder.
It is known that a fiber web, e.g. paper, is manufactured in machines which together constitute a paper-manufacturing line which can be hundreds of meters long. Modern paper machines can produce over 450,000 tons of paper per year. The speed of the paper machine can exceed 2,000 m/min and the width of the fiber web can be more than 11 meters.
In paper-manufacturing lines, the manufacture of paper takes place as a continuous process. A fiber web completing in the paper machine is reeled by a reel-up around a reeling shaft, i.e. a reel spool, into a parent roll the diameter of which can be more than 5 meters and the weight more than 160 tons. The purpose of reeling is to modify the fiber web manufactured as planar to a more easily processable form. On the reel-up located in the main machine line, the continuous process of the paper machine breaks for the first time and shifts into periodic operation.
The web of the parent roll produced in paper manufacture is full-width and even more than 100 km long, so it must be slit into partial webs with suitable width and length for the customers of the paper mill and wound around cores into so-called customer rolls before delivering them from the paper mill. This slitting and winding up of the web takes place in an appropriate separate machine, i.e. a slitter-winder.
On the slitter-winder, the parent roll is unwound, and the wide web is slit on the slitting section into several narrower partial webs which are wound up on the winding section around winding cores, such as spools, into customer rolls. When the customer rolls are completed, the slitter-winder is stopped and the wound rolls, i.e. the so-called set, is removed from the machine. Then, the process is continued with the winding of a new set. These steps, termed a set change, are repeated in sequences periodically until paper runs out of the parent roll, at which point a parent roll change is performed and the operation starts again with the unwinding of a new parent roll.
In the slitter-winders of fiber web machines a fiber web is slit in the longitudinal direction i.e., in the machine direction, into several component webs between a pair of slitter blades comprising a top slitter blade and a bottom slitter blade. The width of the component webs to be slit by the slitter blades and thus the position of the slitter blades can vary to a great extent when different slitter blade settings are used, depending on the set widths of the rolls to be produced. The slitter blades have to be positioned, in the lateral direction i.e., the cross machine direction of the web, in the right slitting position corresponding to the desired roll widths. In order to produce component webs of the desired width the slitter blades of the slitter-winder are spaced apart as desired in the cross machine direction of the paper or board web, that is, a change of settings is carried out.
As to prior art related to the invention, reference is made to U.S. Pat. No. 4,548,105, which discloses a method and a system for observing a position. This publication describes the use of the method in a system used in the slitting of a paper web. In this system to observe the position of the slitting device a measuring device is used which is in a position arrangement which comprises actuating members for controlling and performing the movement of the measuring device in the cross machine direction of the web and which system comprises at least one limiter for limiting the operation of the measuring device along the distance between the extreme positions such that one extreme position serves as the datum position for the determination. An observing device in both directions of movement observes at least one member of the slitting device. The system comprises drive means for the actuating members and moving devices performing a corrective movement of a movable device or member. The position of the slitter blades are determined when the machine is stopped by means of forgoing arrangement, so as to minimize the duration of the standstill.
It is known of prior art to measure the position of slitter blades used in slitting by a carriage-type arrangement, in which a sensor is placed in a moving carriage so the sensor determines by optic or magnetic measurement, the position of the slitter blades. The measurements so determined are used in connection with the changing of slitter blade settings. In DE application publication 102007047890 a device is disclosed that has a magnetic measuring system, in which position detection devices are connected with the carriages of the slitter blades, and a magnetic band which is used to determine position extends over the path of the carriages.
In DE application publication 102007000685 is disclosed an arrangement for position determining of slitter blades of a slitter-winder in which the position determining device comprises a magnetostrictive measuring system integrated in the guides of the slitter blade carriers.
In EP patent publication 1647377 is disclosed a slitter blade arrangement, in which at least one light-emitting element, i.e., a laser, which emits visible radiation is arranged so as to be adjustable, the light beam of the laser is oriented to a desired position for a cutting blade, the laser producing a mark, that is a spot of light, which corresponds to the position to which the cutting blade is to be directed. The laser can be used to produce a fan beam which forms a line in the cutting direction i.e., the machine direction, which marks a selected position for a slitter blade.
In a prior art application using a magnetic measurement, each slitter blade carriage is equipped with a fixed permanent magnet, and the distance between the permanent magnet and the slitter blade is constant, and the position of the permanent magnet is measured by means of a magnetic measuring device, thereby establishing the position of the slitter blade. In connection with the changing of slitter blade settings, information is also needed in addition to the information on the position of the slitter blade carriage. When replacing slitter blades with new blades or after the detachment and grinding of the slitter blades, position information of the distance between the slitter blade edge and the magnet of the slitter blade carriage is needed, without which no exact information on the position of the slitter blade is available based on the results from the measurement methods described above. The slitter blade edge also wears, which leads to inaccuracy when using the above-mentioned measurement methods. In the above-described situations, when prior art applications have been used, there has been a need to carry out so-called tuning runs in order to determine the position of the slitter blade edge.
Such methods and devices for specifying the position of the slitter blades are shown in U.S. Pat. No. 7,086,173 where the slitter blades are arranged in carriages fastened to guides, the position of which is specified. The position of an edge of the bottom slitter blade is calibrated with a separate calibration tool, by bringing the moving calibration tool to the point of the slitting edge of the bottom slitter blade, and the position of the calibration tool is measured. Based on these two measurements (carriage position and calibration tool position), the position of the slitter blade is specified.
In WO publication 2009156566 there is disclosed a method for calibrating the position of slitter blades of a slitter-winder in which there is at least one stationary fixed point of the frame of the slitter-winder. An edge of at least one slitter blade is positioned in relation to the position of the slitter blade carriage. Each fixed point is in the cross machine direction of the frame such that each slitter blade being positioned extends to at least one fixed point. According to one embodiment a sensor measures the position of the edge of the slitter blade with respect to a fixed point. The sensor measures the position of the edge of the slitter blade with respect to the fixed point and the distance between the edge and the slitter blade carriage is specified because the position of the slitter blade carriage is continuously known. Based on knowing the distance between the edge and the slitter blade carriage, the slitter blade can be positioned by positioning the carriage. A variation of this embodiment is disclosed in which the sensor is a distance sensor which measures the position of the slitter blade, preferably the edge, at the moment of calibration. For specifying the position of the slitter blade in this embodiment the slitter blade can be spaced from the sensor.
It is an object of the invention to provide a solution for eliminating or at least minimizing the disadvantages described above.
An object of the invention is to provide an easy-to-use and reliably operating method for calibrating the position of the slitter blades of a slitter-winder.